Keratin, type II cytoskeletal 4 (KRT4)
The protein contains 534 amino acids for an estimated molecular weight of 57285 Da.
No function (updated: Oct. 10, 2018)
Protein identification was indicated in the following studies:
- Bryk and co-workers. (2017) Quantitative Analysis of Human Red Blood Cell Proteome. J Proteome Res. 16(8), 2752-2761.
- D'Alessandro and co-workers. (2017) Red blood cell proteomics update: is there more to discover? Blood Transfus. 15(2), 182-187.
Methods
The following articles were analysed to gather the proteome content of erythrocytes.
The gene or protein list provided in the studies were processed using the ID mapping API of Uniprot in September 2018. The number of proteins identified and mapped without ambiguity in these studies is indicated below.
Only Swiss-Prot entries (reviewed) were considered for protein evidence assignation.
| Publication | Identification 1 | Uniprot mapping 2 | Not mapped / Obsolete | TrEMBL | Swiss-Prot |
|---|---|---|---|---|---|
| Goodman (2013) | 2289 (gene list) | 2278 | 53 | 20599 | 2269 |
| Lange (2014) | 1234 | 1234 | 7 | 28 | 1224 |
| Hegedus (2015) | 2638 | 2622 | 0 | 235 | 2387 |
| Wilson (2016) | 1658 | 1528 | 170 | 291 | 1068 |
| d'Alessandro (2017) | 1826 | 1817 | 2 | 0 | 1815 |
| Bryk (2017) | 2090 | 2060 | 10 | 108 | 1942 |
| Chu (2018) | 1853 | 1804 | 55 | 362 | 1387 |
1 as available in the article and/or in supplementary material
2 uniprot mapping returns all protein isoforms as one entry
The compilation of older studies can be retrieved from the Red Blood Cell Collection database.
The data and differentiation stages presented below come from the proteomic study and analysis performed by our partners of the GReX consortium, more details are available in their published work.
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| Variant | Description |
|---|---|
| allele K4A1 | |
| WSN1 |
No binding partner found
Biological Process
Cornification
Cytoskeleton organization
Epithelial cell differentiation
Keratinization
Negative regulation of epithelial cell proliferation
The reference OMIM entry for this protein is 123940
Keratin 4, type ii; krt4
K4
Kb4
Cytokeratin 4; cyk4; ck4
CLONING
Intermediate filaments are protein polymers which, together with actin filaments and microtubules, form the cytoskeleton of cells. In epithelial cells the intermediate filaments are made up of keratins, a large family of related polypeptides whose patterns of expression vary with cell type as well as with stage of epithelial differentiation. The more than 20 different keratins encoded by at least as many differentially expressed genes in humans (see review by Fuchs, 1988) can be subdivided into 2 classes: type I keratins (K10-K19) are small (40-56.5 kD) and relatively acidic (pI = 4.5-5.5), whereas type II keratins (K1-K9) are larger (53-68 kD) and more basic (pI = 5.5-7.5). Filament formation usually requires expression of keratins in pairs consisting of 1 type I and 1 type II polypeptide. The specific keratins expressed characterize the type of epithelial differentiation. For example, K5 (148040) and K14 (148066) are synthesized in the basal cell layer of all stratified squamous epithelia, while, in the course of stratification, terminally differentiating epidermal cells express K1 (139350) and K10 (148080), and suprabasal cells (i.e., maturing cells of nonkeratinizing squamous epithelia) express K4 and K13 (148065). Using SDS-PAGE, Mischke et al. (1990) identified 2 electrophoretic variants of the human keratin K4 that are expressed in squamous nonkeratinizing epithelia lining the upper digestive tract. Based on a large population sample, they concluded that 2 codominant alleles, a and b, are in Hardy-Weinberg equilibrium and studies in 2 families confirmed the mendelian nature of the variation. They referred to polymorphism also of the K1 and K10 keratins of human epidermis (Mischke and Wild, 1987).MAPPING
Using a cDNA probe in the analysis of human-hamster cell hybrid DNAs, Romano et al. (1987, 1988) mapped the cytokeratin-4 gene to chromosome 12. Barletta et al. (1989, 1990) used in situ hybridization to demonstrate that the cytokeratin-4 gene localizes to human chromosome 12p11.2-q11.MOLECULAR GENETICS
In affected members of 2 Scottish kindreds with white sponge nevus (WSN1; 193900), Rugg et al. (1995) identified heterozygosity for a mutation in the 1A domain of the KRT4 gene (123940.0001). In affected members of an Italian family with WSN1, Terrinoni et al. (2000) identified heterozygosity for a 3-bp insertion in the KRT4 gene (123940.0002). In a Taiwanese patient with WSN1, Chao et al. (2003) identified a heterozygous missense mutation in KRT4 (E449K; 123940.0003). ... More on the omim web site
Oct. 20, 2018: Protein entry updated
Automatic update: OMIM entry 123940 was added.
Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).